We wish to look at DNA and drug adducts in the yeast topoisomerase II structure which we recently determined using data from SSRL. The unliganded HIV-RT crystals we have studied are likewise suitable for soaking DNA fragments and other ligands. We are also attempting to prepare certain co-crystals with synthetic template/primer. We propose to collect heavy-atom derivative data at SSRL. Our crystals of TFIIIA in complex with a 31 bp DNA fragment are "ready" for the synchrotron.